NUCLEATION OF Sb-MICROCRYSTALS IN AN INERT-GAS ATMOSPHERE

The generation of antimony clusters in the size range from Sb to SbSoo is reported. The clusters are created by inert gas condensation and detected by a time-ofiflight mass spectrometer. Condensation of clusters of knvwn sizes onto a cold substrate is suggested as a technique which enables investigations of amorphous substances as a function of order. To reveal the topology of amorphoussolids a variety of model structures have been proposed: Random models, such as the continuous random network model (CRN) for covalent materials and the dense random packed model (DRP) for metals, compete with ordered models, such as the microcrystallite, amorphous cluster models, or the (random) dislocation/stacking models I ) . However, by these theories the amorphous solid is described from extreme points of view, therefore it was suggested to compare structures of amorphous phases of the same substance produced by different methods 2 , , and to develop techniques, by which the extent of order can be determined I). We consider condensation of clusters of known size on a cold substrate to be a possible preparation technique to study properties of amorphous systems as a function of order. In the ticle size 3, . The differences are attributed to antimony evaporating from PtSb predominantly as Sbl atoms, as distinct from Sbq clusters known to evaporate from elementary antimony. Sputtered films 0 (d 2 1000 A) exhibit an electrical resistance which is about one order of magnitude higher compared to the resistance of films evaporated from Sb or PtSh 4, A systematic investigation of amorphous substances composed of clusters as a function of cluster size was hindered so far by the lack of a suitable preparation technique for metallic microclusters (2-500 atoms). Sputtering or adiabatic expansion of metal vapour yield relative cluster intensities which decrease orders of magnitude with increasing cluster size. We present for the first time antimony clusters in the whole size range from Sb, to Sb500, which are generated by inert gas case of antimony, thin amorphous films condensation. The cluster intensities are 0 (thickness d : 70 A) deposited by evapomonitored by a time-of-flight (TOF) mass ration from a PtSb source differ from spectrometer which is especially designed films produced. from elementary antimony for the detection of metal clusters 5 ) . in electrical resistance, light transThe unexpectedly weak decrease of the remission, reaction with oxygen, and parlative cluster intensities yields a size Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980827